According to Thornhill et al. (Aug. 25 issue),1 semen was positive for monkeypox (recently renamed mpox) virus on polymerase-chain-reaction testing in 29 persons. Did the authors analyze prostatic fluid? Semen is not homogeneous and results from at least four exocrine organs and four mucosal exocrine glands. The majority of human immunodeficiency virus (HIV) in semen originates distal to the vas deferens.2 The importance of the prostate reservoir for HIV was shown by Smith et al., who found undetectable seminal plasma HIV RNA in all semen samples obtained without prostatic massage but detectable seminal plasma HIV RNA (≥25 copies per milliliter) in at least one sample obtained after prostatic massage.3 Detailed localization studies of mpox virus are important because the prostate may serve as a reservoir and mpox virus may arise from local replication in the male genitourinary subcompartments.

Second, did the authors observe Trichomonas vaginalis in any of the persons infected with mpox virus? Although T. vaginalis infection is not necessarily a reportable condition, it has been implicated in the pathogenesis of persistent urethritis and prostatitis owing to the postulated phagocytosis and potential killing of Neisseria gonorrhoeae.4T. vaginalis may be an important endocytobiotic agent in the transmission and potential persistence of mpox virus infection in the genitourinary tract.

Jordan Dimitrakoff, M.D., Ph.D.
Food and Drug Administration, Silver Spring, MD
[email protected]

No potential conflict of interest relevant to this letter was reported.

1. Thornhill JP, Barkati S, Walmsley S, et al. Monkeypox virus infection in humans across 16 countries — April–June 2022. N Engl J Med 2022;387:679-691.

2. Krieger JN, Nirapathpongporn A, Chaiyaporn M, et al. Vasectomy and human immunodeficiency virus type 1 in semen. J Urol 1998;159:820-826.

3. Smith DM, Kingery JD, Wong JK, Ignacio CC, Richman DD, Little SJ. The prostate as a reservoir for HIV-1. AIDS 2004;18:1600-1602.

4. Francioli P, Shio H, Roberts RB, Müller M. Phagocytosis and killing of Neisseria gonorrhoeae by Trichomonas vaginalis. J Infect Dis 1983;147:87-94.

The authors reply: The fluid samples that were analyzed in the international case series were semen samples donated by 29 persons; we did not obtain prostatic fluid specifically. Current evidence does not differentiate the source of mpox virus DNA in semen. It may be from seminal carriage originating in the testes, which are an immunologically protected site,1 or from resolving meatal or urethral lesions.2 At least 10 of the 29 persons whose semen samples were positive for mpox DNA also reported penile lesions. Therefore, contamination of semen samples by penile or urethral lesions cannot be ruled out in our case series.

Data on T. vaginalis as a concomitant sexually transmitted infection were not solicited or reported by contributors to our case series — a situation that may reflect the almost exclusively male cohort. In testing guidelines for sexually transmitted infections, testing for T. vaginalis is not routinely recommended for men who have sex with men, other than for persons with persistent penile urethritis.3 Also, the prevalence of T. vaginalis infection has been reported to be five times as high among women as among men.4 We appreciate that T. vaginalis infection may increase the risk of HIV transmission,5 but to date, there is limited evidence regarding the effect of T. vaginalis infection on mpox virus transmission.

John P. Thornhill, M.D., Ph.D.
Queen Mary University of London, London, United Kingdom

Andrea Antinori, M.D.
National Institute for Infectious Diseases Lazzaro Spallanzani IRCCS, Rome, Italy

Chloe M. Orkin, M.D.
Queen Mary University of London, London, United Kingdom
[email protected]

Since publication of their article, the authors report no further potential conflict of interest.

1. Salam AP, Horby PW. The breadth of viruses in human semen. Emerg Infect Dis 2017;23:1922-1924.

2. Palich R, Burrel S, Monsel G, et al. Viral loads in clinical samples of men with monkeypox virus infection: a French case series. Lancet Infect Dis 2022 September 29 (Epub ahead of print).

3. Sherrard J, Pitt R, Hobbs KR, et al. British Association for Sexual Health and HIV (BASHH) United Kingdom national guideline on the management of Trichomonas vaginalis 2021. Int J STD AIDS 2022;33:740-750.

4. Tompkins EL, Beltran TA, Gelner EJ, Farmer AR. Prevalence and risk factors for Trichomonas vaginalis infection among adults in the U.S., 2013–2014. PLoS One 2020;15(6):e0234704-e0234704.

5. McClelland RS, Sangare L, Hassan WM, et al. Infection with Trichomonas vaginalis increases the risk of HIV-1 acquisition. J Infect Dis 2007;195:698-702.